1. Field of the Invention
The present invention is directed to toilet flushing. It finds particular, although not exclusive, application in automatic tank-type flushers.
2. Background Information
The art of toilet flushers is an old and mature one. (We use the term toilet here in its broad sense, encompassing what are variously referred to as toilets, water closets, urinals, etc.) While many innovations and refinements in this art have resulted in a broad range of approaches, flush systems can still be divided into two general types. The first is the gravity type, which is used in most American domestic applications. The gravity type uses the pressure resulting from water stored in a tank to flush the bowl and provide the siphoning action by which the bowl's contents are drawn from it. The second type is the pressurized flusher, which uses line pressure more or less directly to perform flushing.
Some pressure-type flushers are of the tank type. Such flushers employ pressure tanks to which the main water-inlet conduit communicates. Water from the main inlet conduit fills the pressure tank to the point at which air in the tank reaches the main-conduit static pressure. When the system flushes, the water is driven from the tank at a pressure that is initially equal to that static pressure, without reduction by the main conduit's flow resistance. Other pressure-type flushers use no pressure tank, and the main conduit's flow resistance therefore reduces the initial flush pressure.
While flush-mechanism triggering has historically been performed manually, there is also a long history of interest in automatic operation. Particularly in the last couple of decades, moreover, this interest has resulted in many practical installations that have obtained the cleanliness and other benefits that automatic operation affords. As a consequence, a considerable effort has been expended in providing flush mechanisms that are well adapted to automatic operation. Automatic operation is well known in pressure-type flushers of the non-tank variety, but gravity-type flushers and pressurized flushers of the tank variety have also been adapted to automatic operation.
European Patent Publication EPO 0 828 103 A1 illustrates a typical gravity arrangement. The flush-valve member is biased to a closed position, in which it prevents water in the tank from flowing to the bowl. A piston in the valve members shaft is disposed in a cylinder. A pilot valve controls communication between the main (pressurized) water source and the cylinder. When the toilet is to be flushed, only the small amount of energy required for pilot-valve operation is expended. The resultant opening of the pilot valve admits line pressure into the cylinder. That pressure exerts a relatively large force against the piston and thereby opens the valve against bias-spring force. Pilot valves have similarly been employed to adapt pressure-type flushers to automatic operation.